It is disclosed in Japanese Patent Laid Open Sho 53-24400, U.S. Pat. No. 4,400,340 and U.S. Pat. No. 4,426,502 that ring-opening polymerization of a cycloolefin containing norbornene moiety, e.g. dicyclopentadiene (called "DCP" hereinafter), in the presence of a metathesis polymerization catalyst system produces a cross-linked polymer containing olefinic groups in the main chain.
Said Japanese Patent Laid Open Sho 53-24400 is characterized by per se a new metathesis catalyst system, and in it, polymerization of DCP, etc. is accomplished in the presence of a hydrocarbon solvent. DCP polymer prepared therein is recovered from the solvent and then is used to produce a molded article. This means that DCP polymer prepared by using the catalyst system is substantially no-crosslinked non-heat-resistant thermoplastics having a low softening point.
Said U.S. Pat. No. 4,400,340 and U.S. Pat. No. 4,426,502 disclose the production of a molded article by injecting a reactive liquid mixture comprising norbornene-type monomer such as DCP and a metathesis polymerization catalyst system into a mold in which said liquid mixture is metathesis polymerized in bulk (called "RIM process" hereinafter). RIM process is a low pressure one-step or one-shot injection of a liquid mixture into a closed mold where rapid polymerization occurs resulting in a molded article. Thus, there are easily produced large-sized molded articles from DCP and the like by RIM process. The molded articles have been taken notice from the industrial point of view since they have attractive physical properties as balanced in stiffness and impact resistance. However, the molded articles produced from DCP by said RIM process have low softening points generally below 120.degree. C., and this often limits the use of the molded articles produced from DCP, etc.
Further, Japanese Patent Laid Open Sho 61-179214 discloses metathesis copolymerization of norbornene-type cycloolefins such as DCP with other metathesis polymerizable comonomers to produce copolymers having relatively high glass transition temperatures. However, in this case, the attained increase of glass transition temperature is at most about 50.degree. C. and is not enough.
Now, we have found that a mixture comprising the following monomers: ##STR2## or a mixture comprising the following monomers: ##STR3## is readily metathesis polymerized or readily metathesis copolymerized with norbornene-type cycloalkene such as DCP to produce highly cross-linked heat resistant copolymers having a very high softening point.
The mixture comprising the monomers (I-a) and (I-b) is readily obtained as a Diels-Alder adduct of 2 moles of cyclopentadiene with 1 mole of cyclooctadiene. The monomers (I-a) and (I-b) are produced simultaneously in said Diels-Alder reaction, and have the same molecular weight, and are not easily separable each other by usual separation methods such as the fractional distillation. Therefore, in the present invention, the mixture of the monomers (I-a) and (I-b) is used.
The mixture comprising the monomers (II-a) and (II-b) is readily obtained as a Diels-Alder adduct of 2 moles of cyclopentadiene with 1 mole of 1,5-hexadiene. The monomer (II-a) and monomer (II-b) have also the same molecular weight and are not easily separable, and are used as a mixture of them.
Cyclooctadiene and 1,5-hexadiene, the starting materials of the monomers (I-a) and (I-b) or (II-a) and (II-b), are commercially available petrochemical derivatives as well as cyclopentadiene sources.
Therefore, it is an object of the present invention to provide a highly cross-linked heat resistant metathesis polymerized copolymer which is readily and cheaply produced from petroleum products.
A further object is to provide a process for producing said copolymer. Another object is to provide a process for producing a molded article comprising the copolymer. A further object is to provide a polymerizable composition used for producing copolymer and the molded article. Another object is to provide a molded article.